Plastics resistant to UV radiation
Polypedia > Radiation resistant plastics
Plastics resistant to UV radiation | |
Weathering standards for the aging of plastics and polymers. | |
Thermoplastics that are used in outdoor applications are exposed to harsh weather conditions, such as weather, water and sun. Many applications require a weather-resistant thermoplastic material capable of withstanding the effects that UV radiation can have on the appearance and mechanical properties of plastics. UV radiation from sunlight is particularly effective in outdoor applications without protection. Main effects on polymers exposed to UV. All types of UV can have a photochemical effect within the structure of the polymers, which can be beneficial or can cause some type of degradation in the material. Plastics that are inherently resistant are in the group of fluorinated polymers, such as PTFE and PVDF. PTFE has a particularly good resistance to UV radiation caused by strong bonds between carbon and fluorine (C-F). In addition, most fluoropolymers do not have the chromophore impurities that absorb light in their structure and that can act as initiators of photo-oxidation. The types of unmodified plastics with UV additives, whose resistance to UV radiation is considered unacceptable are POM (acetal), PC, ABS and PA6 / 6. Other plastics such as PET, PP, HDPE, PA12, PA11, PA6, PES, PBT, ASA and PPO are considered acceptable. Note that there is a PC / ABS alloy that is also considered acceptable. Without adequate protection measures, different plastic materials begin to yellow and become brittle, depending on the level of irradiation. UV protection is achieved using additives (UV stabilizers) or surface protective coatings (paints, metallization). The addition of carbon black is cost effective, it is used frequently and is a very effective method. Therefore, it is usually advisable that thermoplastics have some type of resistance to UV radiation, in fact to improve their resistance, UV stabilizers are added. Ultraviolet rays can greatly affect materials that are used outdoors and are exposed to the weather. Plastics that are intrinsically resistant to UV radiation will not normally show changes in appearance, such as: Yellowing of the surface Discoloration of the surface with change of tone Crazing Leaching of dyed plastics Increase in fragility due to loss of property Decrease in strength, elasticity and hardness Emergence of stress cracks Normally, the resistance of plastics to UV radiation is achieved through the use of black dye (carbon black is normally used) the addition of carbon black is the most economical and generally very effective way to achieve UV resistant plastics . Additives are also added, such as UV stabilizers (UV absorber or HALS) or perhaps with protective coatings on the surface such as paint, metallized etc. In addition, fluorinated polymers, such as PTFE and PVDF, show a very good stability to UV radiation in their natural state. | |
Note | |
Weather conditions, and in particular UV radiation in outdoor applications, can adversely affect the optical and mechanical properties of plastics. The black color of the plastic is a good way to protect them against these weather influences. On the other hand, the materials of the group of polymers, such as PTFE, ASA and PVDF, show in their natural state a particularly good stability to UV radiation. |